Apoptosis signal-regulating kinase 1 (ASK1), is a member of the mitogen-activated protein kinases (MAPKs) family, which are members of the serine/threonine kinase family. Wang et al. J. Biol. Chem. 1996, 271, 31607-31611, Ichijo et al. Science 1997, 275, 90-94. ASK1 is also known as mitogen-activated protein kinase kinase 5 (MAPKKK5, MAP3K5), MAP/ERK kinase kinase 5 (MEKK5), MEK kinase 5, MEKK5, MAP/ERK kinase kinase 5. The protein kinase composes of 1375 amino acids encompassing 11 kinase subdomains; particularly a serine/threonine kinase domain in the middle part of the molecule with long NH— and COOH-terminal flanking regions. Wang et al. J. Biol. Chem. 1996, 271, 31607-31611, Ichijo et al. Science 1997, 275, 90-94; Tobiume et al. Biochem. Biophys. Res. Commun. 1997, 239, 905-910; U.S. Pat. Nos. 6,080,546 and 6,194,187. The nucleotide sequence of ASK1 is accessible in the protein databases by the accession number NM_005923. ASK1 is ubiquitously expressed with the highest expression in the heart, pancreas, testis, and ovaries.
The MAP kinases mediate signal transduction from the cell surface to the nucleus via phosphorylation cascades. Egan and Weinbery Nature 1993, 365, 781-783.
The MAPK cascades are multifunctional intracellular signaling pathways that are evolutionarily conserved in all eukaryotic cells. Widmann et al. Physiol Rev 1999, 79, 143-180; Kyriakis and Avruch, J. Physiol Rev 2001, 81, 807-869; Ichijo Oncogene 1999, 18:6087-6093. All eukaryotic cells possess multiple MAPK pathways. In mammalian cells, three MAPK cascades that converge on ERKs, c-Jun N-terminal kinases (JNKs), and p38 MAP kinases have been extensively characterized. Egan and Weinbery Nature 1993, 365, 781-783; Boulton et al. Cell 1994, 65, 663-675; and Zhou et al. J. Biol. Chem. 1995, 270, 12665-12669 (the MAPK/ERK pathway); Derujard et al. Cell 1994, 76, 1025-1037; Galcheva-Gargova et al. Science 1994, 265, 806-808; Minden et al. Mol. Cell. Biol. 1994, 14, 6683-6688 (the c-Jun N-terminal kinase (JNK) pathway; and Lee et al. Science 1994, 265, 808-811, (the p38 MAPK pathways). ERK pathway is activated by various growth factors and closely linked to the regulation of cell cycle. The JNK and p38 pathways are preferentially activated by various cytotoxic stress such as UV radiation, X-ray, heat shock, osmotic shock, oxidative stress and pro-inflammatory cytokines such as tumor necrosis factor (TNF) and interleukin-1 Tibbles and Woodgett, Cell Mol, Life Sci. 1999, 55:1230-1254. JNK and p38 are thus also called stress-activated protein kinases (SAPKs).
Each MAPK cascade involves three classes of serine/threonine kinases, MAPK, MAPK kinanse (MAP2K) and MAP2K kinase (MAP3K). In the MAPK signaling cascades, MAP3K phosphorylates and thereby activates MAP2K in turn phosphorylates and activates MAPK. Activated MAPK may translocate to the cell nucleus and regulate the activities of transcription factors and thereby control gene expression. Sturgill and Wu, Biochim. Biophys. Acta 1993, 1092, 350; Nishida and Gotoh, Trends Biochem. Sci. 1993, 18, 128; Errede and Levin Curr. Opin. Cell Biol. 1993, 5, 254; Marshall Curr. Opin. Genet. Dev. 1994, 82.
MAP3Ks play pivotal roles in sensing and signaling of cellular and environmental stress. The MAP3Ks in the JNK and p38 pathways are highly divergent in number and structure. At least eleven MAP3Ks have been identified upstream of JNK, each of which activates single or multiple downstream MAPK cascades. This diversity and complexity are consistent with the variety of stimuli that activate MAPK pathways. Kyriakis and Avruch Physiol. Rev. 2001, 81, 807-869.
One of the important biological responses mediated through these stress-activated MAP kinase pathways appears to be the decision of cell fate by regulating apoptosis. The possible roles of the JNK pathway in pro-apoptosis signaling have been demonstrated by knockout mouse studies. Yang et al. Nature 1997, 389:865-870; Sabapathy et al. Curr. Biol. 1999, 9:116-125; Kuan et al. Neuron 1999, 22:667-676. Several lines of evidence have also suggested the pro-apoptotic roles of the p38 pathway. Xia et al. Science 1995, 270:1326-1331; Kawaski et al. J. Biol. Chem. 1997, 272:18518-18521; Harper and LoGrasso et al. Cell Signal. 2001, 13:299-310.
ASK1 was originally identified as an apoptosis-inducing MAP3K. ASK1 regulates the p38 and JNK pathways by directly phosphorylating and thereby activating their respective MAPKKs, MKK4(SEK1)/MKK7 and MKK3/MKK6. Wang et al. J. Biol. Chem. 1996, 271, 31607-31611; Ichijo et al. Science 1997, 275, 90-94. The activity of ASK1 is tightly regulated; a ubiquitously expressed reduction/oxidation protein thioredoxin (Trx) binds to the N-terminal and inhibits its activity. ASK1 is activated by various cytotoxic stresses including oxidative stress, endoplasmic reticulum (ER) stress, and calcium overload, and by receptor-mediated inflammatory signals such as tumor necrosis factor (TNF) and endotoxic lipopolysaccharide (LPS). Hayakaw et al. Microbes and Infection 2006, 8, 1098-1107; Saitoh et al EMBO J. 1998, 17:2596-2606; Nishitoh et al. Genes Dev. 2002, 16:1345-1355; Takeda et al. EMBO Rep. 2004, 5, 161-166; Nishitoh et al. Mol Cell 1998, 2,389-395; Matsukawa et al. Nat Immunol 2005, 6, 587-592. It has been shown that ASK1 is required for apoptosis induced by oxidative stress, TNF and ER stresses. Nishitoh et al. Genes Dev. 2002, 16:1345-1355; Matsukawa et al. Nat Immunol 2005, 6, 587-592; Tobiume et al. EMBO Rep. 2001, 2:222-228. Overexpression of wild-type or constitutively active ASK1 induces apoptosis in various cells through mitochondria-dependent caspase activation. Saitoh et al EMBO J. 1998, 17:2596-2606; Kanamoto et al. Mol. Cell. Biol. 2000, 20, 196-204; Hatai et al. J. Biol. Chem. 2000, 275, 26576-26588.
Recent studies revealed that ASK1 contributes not only to regulation of cell death but also has diverse functions in the decision of cell fate such as cytokine responses, cell differentiation, and innate immune responses. Matsukawa et al. J. Biochem. (Toyko) 2004, 136, 261-265. Sayama et al. J. Biol. Chem. 2000, 276:999-1004; Takeda et al. J. Biol. Chem. 2000, 275:9805-9813; Sagasti et al. Cell 2001, 105:221-232; Kim et al. Science 2002, 297:623-626; Nishitoh et al. Genes Dev. 2002, 16:1345-1355; Matsukawa et al. Nat Immunol 2005, 6, 587-592; Tobiume et al. EMBO Rep. 2001, 2:222-228; Imoto, et al. Diabetes 2006, 55:1197-1204. Constitutively active ASK1 induces neurite outgrowth in PC12 cells. ASK1 is activated by CaMKII, which activates ASK1-p38 pathway in neurons, suggesting that ASK1 might play critical roles in synaptic plasticity. Moreover, TRAF6-ASK1-p38 pathway plays an essential role in inflammatory and innate immune responses. Hayakawa et al. Microbes and Infection 2006, 8, 1098-1107. It has also been demonstrated that ASK1 has a role in the pathogenesis of TNF-α-induced insulin resistance. Overexpression of wild-type ASK1 increases serine phosphorylation of insulin receptor substrate (IRS)-1, and decreases insulin-stimulated tyrosine phosphorylation of IIRS-1, leading to impair insulin signaling. Imoto, et al. Diabetes 2006, 55:1197-1204.
ASK1 is thus a pivotal component not only in stress-induced cell death but also in a broad range of biological activities in order for cells to adapt to or oppose various stresses. Modulating the activity of ASK1 potentially have beneficial effect in treating or preventing a wide range of diseases and conditions including, but not limited to, cardiovascular diseases, inflammatory diseases, autoimmune diseases, destructive bone disorders, neurodegenerative disorders, and metabolic diseases such as diabetes. Thompson, Science 1995, 267, 1456-1462; Yuan and Yanker Nature 2000, 407, 802-809; Los et al. Immunity 1999, 10, 629-639.
Currently, there are no known therapeutical agents that effectively inhibit the expression and/or activation of ASK1, and to date, strategies aimed at modulating ASK1 function have involved the use of antibodies, dominant negative and dominant active mutants of the protein.
U.S. Pat. No. 5,981,265 and No. 6,074,861 claim methods for regulating MAP3K protein activity in a cell by transforming or transfecting the cell with a nucleic acid that is capable of hybridizing under stringent conditions to a nucleic acid molecule encoding MAP3K1, MAP3K2, MAP3K3, MAP3K4, MAP3K5, and MAP3K6. Oligonucleotides for use in antisense, and triplex formation, as ribozymes, probes or primers and in other applications are generally disclosed. WO 01/07461 discloses antisense compositions and methods for using the antisense compositions to modulate the expression of MAP3K5 and treat diseases associated with expression of MAP3K5.
Consequently, there remains a long felt need for agents capable of effectively modulating the activity of ASK1. A small molecule inhibitor may be proof to be an effective means for regulating ASK1 activities.